Pad-equipped thermocouple and method for producing sheath thermocouple used therein

ABSTRACT

A pad-equipped thermocouple includes a sheathed thermocouple in which a pair of thermocouple elements and an inorganic insulating powder for holding the thermocouple elements are accommodated in a sheath. An opening of the sheath is sealed by a sealing member. A pad is welded to a pipe and configured to hold the sheathed thermocouple to a surface of the pipe. A temperature measuring junction formed by the pair of thermocouple elements is exposed to a side face of the sheath in a leading end portion. The pad includes an accommodation portion accommodating the leading end portion such that the leading end portion can be inserted into and pulled out from the accommodation portion along the surface of the pipe, and the accommodation portion accommodates the leading end portion in a state where the temperature measuring junction and the surface of the pipe are in contact with each other.

TECHNICAL FIELD

The present invention relates to a pad-equipped thermocouple whichmeasures the surface temperature of a measurement target object by beingin contact therewith, and relates to a method for producing a sheathedthermocouple to be used therein.

BACKGROUND ART

In a case where the surface temperature of a device such as a pipe or acontainer is to be measured by use of a sheathed thermocouple havingthermocouple elements accommodated in a metal tube with inorganicinsulating powder provided therein, a pad-equipped thermocouple is usedin which a metal pad to be fixed to the surface of a measurement targetobject such as a pipe or a container is provided at the leading end of asheathed thermocouple. PATENT LITERATURE 1 and PATENT LITERATURE 2 belowdisclose such pad-equipped thermocouples.

CITATION LIST Patent Literature

PATENT LITERATURE 1: Japanese Utility Model Registration No. 3108015

PATENT LITERATURE 2: U.S. Pat. No. 5,382,093

SUMMARY OF INVENTION Technical Problem

According to a pad-equipped thermocouple described in PATENT LITERATURE1 above, while the thermocouple elements are protected from the externalenvironment, the temperature measuring junction is in direct contactwith a measurement target object. Accordingly, the pad-equippedthermocouple is less likely to be influenced by the ambient airtemperature, and thus, the surface temperature of the measurement targetobject can be accurately measured.

A pad-equipped thermocouple described in PATENT LITERATURE 2 above isconfigured such that a sheathed thermocouple is inserted in a guide tubewelded to a metal pad, and the sheathed thermocouple can be easilyattached and detached.

In general, since a thermocouple is exposed to a high temperatureenvironment for a long period, there are cases where properties thereofare deteriorated due to aging. Such a thermocouple of which propertieshave been deteriorated due to aging needs to be replaced in order tomaintain measurement accuracy.

However, in the pad-equipped thermocouple described in PATENT LITERATURE1 above, the leading ends of a pair of thermocouple elements are weldedso as to seal a hole formed in the surface of the metal pad, therebyproviding a temperature measuring junction. In addition, this metal padis welded and fixed to the surface of the measurement target object suchthat the temperature measuring junction is in contact with the surfaceof the measurement target object.

Therefore, when the sheathed thermocouple is deteriorated and needs tobe replaced, the thermocouple elements need to be dismounted after thewelded and fixed metal pad is dismounted from the measurement targetobject, which is troublesome.

Further, when the metal pad fixed by welding is to be dismounted fromthe measurement target object, there is a risk that a pipe or acontainer, which is the measurement target object, is thermallyinfluenced or damaged.

This requires a test to be performed for evaluating whether there is noproblem in the performance of the pipe, the container, or the like afterthe metal pad has been dismounted. Thus, in general and in actuality, apad-equipped thermocouple is newly mounted without the metal pad beingdismounted.

Therefore, in the case of the pad-equipped thermocouple described inPATENT LITERATURE 1 above, even when the sheathed thermocouple isdeteriorated and needs to be replaced, a whole pad-equipped thermocoupleneeds to be newly provided at a position on a surface at which thenewly-provided pad-equipped thermocouple does not interfere with thepad-equipped thermocouple that needs to be replaced.

Meanwhile, according to the pad-equipped thermocouple described inPATENT LITERATURE 2 above, since the sheathed thermocouple is easilyattached and detached, the problem as in PATENT LITERATURE 1 does notoccur.

However, the sheathed thermocouple of PATENT LITERATURE 2 is configuredsuch that the sheathed thermocouple is inserted in the guide tube andperforms temperature measurement in a state where the guide tube and themetal pad are interposed between the sheathed thermocouple and themeasurement target object, and unlike the pad-equipped thermocoupledescribed in PATENT LITERATURE 1 above, the temperature measuringjunction is not in direct contact with the measurement target object.Therefore, the sheathed thermocouple of PATENT LITERATURE 2 is easilyinfluenced by the ambient air temperature, and there is a risk of thiscausing a decrease in the measurement accuracy of the surfacetemperature of the measurement target object.

Thus, with conventional pad-equipped thermocouples, it is difficult torealize both of: making the pad-equipped thermocouple less likely to beinfluenced by the ambient air temperature, thereby accurately measuringthe surface temperature of the measurement target object; and improvingmaintainability that the thermocouple can be easily replaced.

The present invention has been made in view of such circumstances. Anobject of the present invention is to provide a pad-equippedthermocouple that can perform accurate temperature measurement and thatcan improve maintainability, and a method for producing a sheathedthermocouple to be used therein.

Solution to Problem

(1) A pad-equipped thermocouple of the present invention is apad-equipped thermocouple including: a sheathed thermocouple in which atleast a pair of thermocouple elements and an inorganic insulating powderfor holding the thermocouple elements are accommodated in a sheath, andan opening in a leading end of the sheath is sealed by a sealing memberbeing welded to the leading end of the sheath; and a pad welded to atemperature measurement target object and configured to hold thesheathed thermocouple at a surface of the temperature measurement targetobject, wherein a temperature measuring junction formed by the pair ofthermocouple elements is provided so as to be exposed at a sheath sideface of a leading end portion of the sheathed thermocouple, the padincludes an accommodation portion configured to accommodate the leadingend portion of the sheathed thermocouple such that the leading endportion can be inserted into and pulled out from the accommodationportion along the surface of the temperature measurement target object,and the accommodation portion accommodates the leading end portion ofthe sheathed thermocouple in a state where the temperature measuringjunction and the surface of the temperature measurement target objectare in contact with each other.

According to the pad-equipped thermocouple configured as describedabove, the temperature measuring junction is provided so as to beexposed at the sheath side face of the leading end portion of thesheathed thermocouple, and the leading end portion of the sheathedthermocouple is accommodated in the accommodation portion in a statewhere the temperature measuring junction and the surface of themeasurement target object are in contact with each other. Accordingly,the pad-equipped thermocouple is less likely to be influenced by theambient air temperature, and thus, can accurately measure the surfacetemperature of the measurement target object. In addition, the leadingend portion of the sheathed thermocouple is accommodated in theaccommodation portion of the pad such that the leading end portion canbe inserted into and pulled out from the accommodation portion. Thus, ifthe leading end portion is pulled out from the accommodation portion,the sheathed thermocouple can be easily dismounted from the pad.

As described above, according to the pad-equipped thermocouple havingthe configuration described above, the surface temperature of themeasurement target object can be accurately measured, and thethermocouple can be easily replaced. Thus, maintainability can beimproved.

(2) Preferably, in the pad-equipped thermocouple described above, thesheath side face of the leading end portion of the sheathed thermocouplehas formed therein a hole portion for allowing the temperature measuringjunction to be exposed therethrough, the hole portion is formed at apredetermined interval from an end face of the leading end, of thesheath, which has the sealing member welded thereto, the temperaturemeasuring junction is formed as a weld portion obtained by weldingleading ends of the pair of thermocouple elements to each other, and thehole portion is sealed by the weld portion.

In this case, the temperature measuring junction can be formed at aposition apart from the sealing member. Therefore, when the sealingmember is to be fixed to the leading end face of the sheath, influence,such as degeneration due to heat, on the temperature measuring junctioncan be alleviated.

(3) In the pad-equipped thermocouple described above, the sheathedthermocouple may include: a first bar-shaped portion having, at one endthereof, the leading end portion; and a second bar-shaped portionconnected to an other end of the first bar-shaped portion and extendingin a direction that crosses an extending direction of the firstbar-shaped portion in a state where the second bar-shaped portion is incontact with the temperature measurement target object, and the secondbar-shaped portion may be fixed to the surface of the temperaturemeasurement target object by a fixing plate configured to fix thesheath.

In this case, the fixing plate can prevent the first bar-shaped portionfrom rotating about the axis extending along the longitudinal directionof the first bar-shaped portion. As a result, the temperature measuringjunction can be caused to be reliably in contact with the surface of themeasurement target object.

(4) The pad-equipped thermocouple described above may be configured suchthat the leading end portion has an outer peripheral shape which is adeformed shape which is not a circular shape, and the accommodationportion has an inner peripheral shape which is a shape that correspondsto the outer peripheral shape of the leading end portion, therebypreventing the leading end portion from rotating about an axis extendingalong a longitudinal direction. It should be noted that the innerperipheral shape of the accommodation portion means the shape of theinner periphery in a radial cross section of the accommodation portion.The outer peripheral shape of the leading end portion means the shape ofthe outer periphery in a radial cross section of the sheath.

(5) In the pad-equipped thermocouple described above, the innerperipheral shape of the accommodation portion and the outer peripheralshape of the leading end portion of the sheathed thermocouple may beeach formed in any of a closed curve shape other than a circular shape,a semicircular shape, and a polygonal shape, and the inner peripheralshape of the accommodation portion and the outer peripheral shape of theleading end portion of the sheathed thermocouple may be made to be thesame with each other so as not to cause a gap between an innerperipheral face of the accommodation portion and an outer peripheralface of the leading end portion of the sheathed thermocouple and theaccommodation portion may accommodate the leading end portion so as tobe fitted to each other.

In this case, the accommodation portion can prevent the leading endportion of the sheathed thermocouple from rotating about the axisextending along the longitudinal direction. As a result, the temperaturemeasuring junction can be caused to be reliably in contact with thesurface of the measurement target object.

(6) A method for producing the sheathed thermocouple to be used in thepad-equipped thermocouple according to (1) to (5) above includes: a stepof removing a leading end section of a first sheath member and theinorganic insulating powder in the leading end section of the firstsheath member from a sheathed thermocouple base material in which atleast the pair of thermocouple elements and the inorganic insulatingpowder for holding the thermocouple elements are accommodated in thefirst sheath member, and of causing leading end portions of the pair ofthermocouple elements to be exposed; a step of forming, in a side faceof a second sheath member which is to be abutted and connected to thefirst sheath member, a hole portion which allows communication betweeninside and outside of the second sheath member; a step of inserting theleading end portions of the pair of thermocouple elements into the holeportion from inside of the second sheath member; a step of forming thesheath by causing an end face of the first sheath member and one endface of the second sheath member to be abutted and welded to each other,forming the temperature measuring junction exposed toward the outside ofthe second sheath member through the hole portion by welding, at thehole portion, the leading ends of the pair of thermocouple elements toeach other, and filling the inorganic insulating powder into the secondsheath member through the opening in the leading end of the sheath aftersealing the hole portion by welding; and a step of sealing the openingby welding the sealing member to the opening in the leading end of thesheath.

According to the method for producing the sheathed thermocoupleconfigured as described above, the leading end portions of the pair ofthermocouple elements are caused to be exposed, and the temperaturemeasuring junction exposed from the hole portion is formed by weldingthe pair of thermocouple elements to each other at the hole portionformed in the second sheath member, and then, the first sheath memberand the second sheath member are welded to each other. Therefore, forexample, when compared with a case where work is performed while thepair of thermocouple elements are handled within the sheath without thepair of thermocouple elements being exposed to the outside, workabilityat the time of forming the temperature measuring junction exposed at theside face of the sheath is good, and thus, production efficiency can beimproved.

Advantageous Effects of Invention

According to the present invention, temperature measurement can beaccurately performed and maintainability can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a pad-equipped thermocouple according to afirst embodiment of the present invention.

FIG. 2 is a cross-sectional view of the vicinity of a pad of thepad-equipped thermocouple.

FIG. 3 is a cross-sectional view along the A-A arrows in FIG. 2.

FIG. 4 is diagrams showing a method for producing a sheathedthermocouple according to the pad-equipped thermocouple of the firstembodiment.

FIG. 5 is diagrams showing the method, for producing the sheathedthermocouple according to the pad-equipped thermocouple of the firstembodiment, which is continued from the method shown in FIG. 4.

FIG. 6 is a perspective view showing a leading end portion 4 of asheathed thermocouple 3 of a pad-equipped thermocouple according to asecond embodiment.

FIG. 7 is a cross-sectional view of the part in FIG. 6, that correspondsto the part along the A-A arrows in FIG. 2.

FIG. 8 is a diagram showing a variation of arrangement of thepad-equipped thermocouple.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferable embodiments are described with reference to thedrawings.

FIG. 1 is a diagram showing a pad-equipped thermocouple according to afirst embodiment of the present invention.

In FIG. 1, a pad-equipped thermocouple 1 is mounted to a cylindricalpipe P as a temperature measurement target object of which surfacetemperature is to be measured.

The pad-equipped thermocouple 1 includes a pad 2 and a sheathedthermocouple 3 extending from the pad 2.

The pad 2 is a member formed from a stainless steel, a heat resistingsteel, or the like, and holds the sheathed thermocouple 3 at a surfacep1 of the pipe P by accommodating a leading end portion 4 of thesheathed thermocouple 3 therein.

The sheathed thermocouple 3 forms a temperature sensor for measuring thesurface temperature of the pipe P. The sheathed thermocouple 3 includes:a first bar-shaped portion 3 a which has the leading end portion 4 atone end thereof and which extends in a bar shape in the axial directionof the pipe P along the surface p1 of the pipe P; a second bar-shapedportion 3 b one end of which is connected to the other end of the firstbar-shaped portion 3 a and which extends, along the surface p1 of thepipe P, in a bar shape in a direction that crosses the extendingdirection of the first bar-shaped portion 3 a; and a third bar-shapedportion 3 c one end of which is connected to the other end of the secondbar-shaped portion 3 b and which extends, along the surface p1 of thepipe P, in a bar shape in the axial direction of the pipe P.

Each bar-shaped portion 3 a, 3 b, 3 c is formed by bending a singlebar-shaped sheathed thermocouple at a predetermined position.

Each bar-shaped portion 3 a, 3 b, 3 c is disposed in a state of being incontact with the surface p1 of the pipe P.

The first bar-shaped portion 3 a is held at the surface p1 of the pipe Pby the leading end portion 4 being accommodated in the pad 2. The secondbar-shaped portion 3 b is held at the surface p1 of the pipe P by afirst sheath fixing plate 5 welded and fixed to the surface p1. Thethird bar-shaped portion 3 c is held at the surface p1 of the pipe P bya second sheath fixing plate 6 welded and fixed to the surface p1.

Thus, the sheathed thermocouple 3 is held at the surface p1 of the pipeP by the sheath fixing plates 5 and 6 in addition to the pad 2.

This prevents the temperature measuring junction of the sheathedthermocouple 3 from rotating about the axis and thus being displaced.Therefore, the temperature measuring junction can be caused to bereliably in contact with the surface p1 of the pipe P.

Both the sheath fixing plates 5 and 6 are plate members formed from astainless steel or the like, respectively have one end thereof beingwelded and fixed to the surface p1 of the pipe P, and are formed in suchshapes that respectively press the second bar-shaped portion 3 b and thethird bar-shaped portion 3 c to the surface p1 side. Accordingly, thesheath fixing plates 5 and 6 hold the second bar-shaped portion 3 b andthe third bar-shaped portion 3 c at the surface p1, respectively.

At one end of each of the sheath fixing plates 5 and 6, weld portions 5a and 6 a are formed, respectively. The one ends of the sheath fixingplates 5 and 6 are welded and fixed to the surface p1. Meanwhile, theother ends of the sheath fixing plates 5 and 6 are not welded or fixedto the surface p1, and are in a free state. Further, the sheath fixingplates 5 and 6 have plate thicknesses that allow easy deformationthereof.

Accordingly, if external force is applied to the sheath fixing plates 5and 6 so as to be deformed to open, thereby cancelling the holding ofthe second bar-shaped portion 3 b and the third bar-shaped portion 3 c,the sheathed thermocouple 3 can be easily dismounted from the pad 2 andthe pipe P.

When the sheathed thermocouple 3 is to be mounted again, the leading endportion 4 of the first bar-shaped portion 3 a is accommodated in the pad2 so as to be in contact with the surface p1 of the pipe P, the sheathfixing plates 5 and 6 are deformed into their original states byexternal force so as to hold the second bar-shaped portion 3 b and thethird bar-shaped portion 3 c, respectively. Accordingly, the sheathedthermocouple 3 that has been dismounted once can be mounted again.

FIG. 2 is a cross-sectional view of the vicinity of the pad 2 of thepad-equipped thermocouple 1, and FIG. 3 is a cross-sectional view alongthe A-A arrows in FIG. 2.

The pad 2 has formed therein an accommodation portion 2 a whichaccommodates the leading end portion 4 of the sheathed thermocouple 3 soas to cover the leading end portion 4.

In the sheathed thermocouple 3, the leading end portion 4, which is thepart thereof accommodated in the accommodation portion 2 a, is incontact with the surface p1 of the pipe P in a state where the leadingend portion 4 is accommodated in the accommodation portion 2 a.

The sheathed thermocouple 3 includes: a pair of thermocouple elements 10a and 10 b; a temperature measuring junction 10 c which connects theleading ends of the pair of thermocouple elements 10 a and 10 b to eachother; a sheath 11 which accommodates the thermocouple elements 10 a and10 b; an inorganic insulating powder 12 filling the sheath 11; and asealing member 13 which seals the opening at the leading end of thesheath 11.

The sheath 11 is a cylindrical tubular member formed from a stainlesssteel or a heat resisting alloy, for example, and protects thethermocouple elements 10 a and 10 b accommodated therein from theexternal environment.

The sheath 11 is formed by connecting a sheath 21 (first sheath member)and a sleeve 30 (second sheath member) having the sealing member 13fixed thereto as described later.

As the inorganic insulating powder 12, an inorganic material powder suchas magnesium oxide (MgO), aluminium oxide (Al₂O₃), or the like is used,for example. By filling the sheath 11, the inorganic insulating powder12 holds the thermocouple elements 10 a and 10 b in the sheath 11.

As described above, the sheathed thermocouple 3 extends, having aconfiguration in which the thermocouple elements 10 a and 10 b areaccommodated in the sheath 11. Thus, the second bar-shaped portion 3 band the third bar-shaped portion 3 c of the sheathed thermocouple 3 alsohave a similar configuration.

The sealing member 13 is a disc-like member formed from a stainlesssteel or a heat resisting alloy, and is welded and fixed to a leadingend face 11 a of the sheath 11. Accordingly, the sealing member 13 sealsan opening 11 d of the leading end face 11 a of the sheath 11 such thatthe inorganic insulating powder 12 in the sheath 11 does not leak to theoutside.

The thermocouple elements 10 a and 10 b are blocked from the externalatmosphere by the inorganic insulating powder 12 and the sealing member13, and are protected from external environments such as a mechanicalimpact and a corrosive atmosphere. In addition, occurrence ofmeasurement errors due to reduced insulation of the inorganic insulatingpowder caused by entry of moisture from outside is prevented.

A hole portion 11 b is formed in a side face 11 c of the sheath 11 atthe leading end portion 4 of the sheathed thermocouple 3. The holeportion 11 b is formed at a predetermined interval in the axialdirection from the leading end face 11 a having the sealing member 13welded thereto. The hole portion 11 b is formed so as to allowcommunication between the inside and the outside of the sheath 11. Thehole portion 11 b is formed in an abutment face 11 c 1, of the side face11 c of the sheath 11, that is in contact with the surface p1 of thepipe P.

As described above, the pair of thermocouple elements 10 a and 10 b areaccommodated in the sheath 11 along the longitudinal direction of thesheath 11. Of the pair of thermocouple elements 10 a and 10 b, if, forexample, one thermocouple element 10 a serves as the thermocoupleelement at the positive side, the other thermocouple element 10 b servesas the thermocouple element at the negative side.

The temperature measuring junction 10 c is a member for detecting thetemperature of the surface p1 of the pipe P, and is formed as a weldportion which is obtained by welding the leading ends of the pair ofthermocouple elements 10 a and 10 b to each other. The weld portionseals the hole portion 11 b, and prevents the inorganic insulatingpowder 12 in the sheath 11 from leaking.

As described above, the temperature measuring junction 10 c is providedso as to extend, from the inner side of the sheath 11 and through thehole portion 11 b, to be exposed to the outer side of the sheath 11. Thehole portion 11 b is formed in the abutment face 11 c 1 which is incontact with the surface p1 of the pipe P as described above. Therefore,the temperature measuring junction 10 c is provided so as to be exposedat the abutment face 11 c 1.

In addition, the temperature measuring junction 10 c is formed so as tobe in contact with the surface p1 of the pipe P.

Thus, since the temperature measuring junction 10 c is provided so as tobe exposed at the abutment face 11 c 1 of the sheath 11 and is incontact with the surface p1 of the pipe P, the sheathed thermocouple 3can accurately measure the surface temperature of the pipe P.

The pad 2 is a substantially cylindrical hollow member having theaccommodation portion 2 a formed therein, and is welded and fixed in astate where a contact face 2 b is in contact with the surface p1 of thepipe P.

The pad 2 and the pipe P are welded to each other from outside along theboundary therebetween. Thus, in the boundary part between the surface ofthe pad 2 and the surface p1, a weld bead B is formed along thelongitudinal direction of the pad 2.

The accommodation portion 2 a formed in the pad 2 has a shape thatcorresponds to the outer peripheral shape in a radial cross section ofthe sheath 11 (hereinafter, referred to as outer peripheral shape), theinner peripheral shape in a radial cross section of the accommodationportion 2 a (hereinafter, referred to as inner peripheral shape) issubstantially circular, and the accommodation portion 2 a is formed in ahole shape. The inner peripheral shape of the accommodation portion 2 aand the outer peripheral shape of the sheath 11 have the same shapealong the axial direction, and further, an inner diameter dimension D ofthe accommodation portion 2 a is set to be such a dimension thatprovides a clearance that allows the sheath 11 to be inserted into andpulled out from the accommodation portion 2 a. Thus, the accommodationportion 2 a accommodates the leading end portion 4 of the sheathedthermocouple 3 such that the leading end portion 4 can be inserted intoand pulled out from the accommodation portion 2 a along the surface p1of the pipe P.

At the contact face 2 b side of the pad 2, an exposure opening 2 c,which is open along the longitudinal direction of the sheath 11, isformed in a slit shape.

Through this exposure opening 2 c, the accommodation portion 2 a allowsthe side face 11 c of the sheath 11 to be exposed to the pipe P, and theaccommodation portion 2 a accommodates the leading end portion 4 of thesheathed thermocouple 3 in a state where the temperature measuringjunction 10 c exposed from the sheath 11 and the surface p1 of the pipeP are in contact with each other.

Here, a width dimension W (FIG. 3) of the exposure opening 2 c is set toa dimension smaller than the inner diameter dimension D of theaccommodation portion 2 a. Accordingly, for example, when compared witha case where the width dimension W of the exposure opening 2 c isgreater than or equal to the inner diameter dimension D, the innerperipheral shape of the accommodation portion 2 a becomes a shape thatcorresponds to the outer peripheral shape of the sheath 11, and theaccommodation portion 2 a can hold the side face 11 c up to a positioncloser to the abutment face 11 c 1 of the sheath 11. As a result, theaccommodation portion 2 a can hold the side face 11 c of the sheath 11in a greater range, and thus, can hold the sheath 11 (the sheathedthermocouple 3) more stably.

According to the pad-equipped thermocouple 1 having the configurationdescribed above, the temperature measuring junction 10 c is provided soas to be exposed at the side face 11 c (the abutment face 11 c 1) of theleading end portion 4 of the sheathed thermocouple 3, and the leadingend portion 4 of the sheathed thermocouple 3 is accommodated in theaccommodation portion 2 a in a state where the temperature measuringjunction 10 c and the surface p1 of the pipe P are in contact with eachother. Accordingly, the pad-equipped thermocouple 1 is less likely to beinfluenced by the ambient air temperature, and thus, can accuratelymeasure the surface temperature of the pipe P. In addition, the leadingend portion 4 of the sheathed thermocouple 3 is accommodated in theaccommodation portion 2 a of the pad 2 such that the leading end portion4 can be inserted into and pulled out from the accommodation portion 2a. Therefore, if the leading end portion 4 is pulled out from theaccommodation portion 2 a, the sheathed thermocouple 3 can be easilydismounted from the pad 2.

Further, if the first sheath fixing plate 5 and the second sheath fixingplate 6 are deformed into their original states by external force suchthat the second bar-shaped portion 3 b and the third bar-shaped portion3 c are released from the pipe P, the sheathed thermocouple 3 can beeasily dismounted from the pipe P.

As described above, according to the pad-equipped thermocouple 1 havingthe configuration described above, the surface temperature of the pipe Pcan be accurately measured, the sheathed thermocouple 3 can be easilyreplaced, and maintainability can be improved.

In the present embodiment, since the hole portion 11 b is formed at apredetermined interval from the leading end face 11 a of the sheath 11,the temperature measuring junction 10 c can be formed at a position awayfrom the sealing member 13. Therefore, when the sealing member 13 is tobe welded to the leading end face 11 a of the sheath 11, influence, suchas degeneration due to heat, on the temperature measuring junction 10 ccan be alleviated.

In the present embodiment, the sheathed thermocouple 3 is configured toinclude: the first bar-shaped portion 3 a having, at one end thereof,the leading end portion 4 of the sheathed thermocouple 3; and the secondbar-shaped portion 3 b which is connected to the other end of the firstbar-shaped portion 3 a and which extends, in a state of being in contactwith the pipe P, in a direction that crosses the extending direction ofthe first bar-shaped portion 3 a. Therefore, the second bar-shapedportion 3 b can prevent the first bar-shaped portion 3 a from rotatingabout the axis extending along the longitudinal direction of the firstbar-shaped portion 3 a. As a result, the temperature measuring junction10 c can be caused to be reliably in contact with the surface p1 of thepipe P.

FIG. 4 and FIG. 5 are diagrams showing a method for producing thesheathed thermocouple 3 of the present embodiment. In FIG. 4 and FIG. 5,the sleeve 30 and the inorganic insulating powder 12 are expressed in atransparent manner so as to show the disposed state of the thermocoupleelements 10 a and 10 b, the temperature measuring junction 10 c, and thehole portion 11 b in the inner space of the sleeve 30.

As described above, the sheathed thermocouple 3 is provided such thatthe temperature measuring junction 10 c is exposed at the side face 11 c(the abutment face 11 c 1) of the sheath 11. In order to produce such asheathed thermocouple 3, a sheathed thermocouple not yet provided withthe temperature measuring junction 10 c connecting the pair ofthermocouple elements 10 a and 10 b to each other (hereinafter, alsoreferred to as sheathed thermocouple base material) is used.

(a) of FIG. 4 is a perspective view showing a sheathed thermocouple basematerial.

In (a) of FIG. 4, a sheathed thermocouple base material 20 is configuredsuch that the pair of thermocouple elements 10 a and 10 b, and theinorganic insulating powder 12 for holding the thermocouple elements 10a and 10 b are accommodated in the sheath 21 (first sheath member).

In order to produce the sheathed thermocouple 3 by use of the sheathedthermocouple base material 20, first, a leading end section 22 of thesheath 21, and the inorganic insulating powder 12 in the leading endsection 22 are removed from the sheathed thermocouple base material 20,whereby the leading end portions of the pair of thermocouple elements 10a and 10 b are exposed.

(a) of FIG. 4 indicates the leading end section 22 by broken lines, andshows a state where the leading end section 22 and the inorganicinsulating powder 12 therein have been removed and the pair ofthermocouple elements 10 a and 10 b are exposed. At this time, thesheath 21 is filled with the inorganic insulating powder 12.

Next, the hole portion 11 b which allows communication between theinside and the outside of the sleeve 30 is formed in the side face ofthe sleeve 30 (second sheath member) that is to be abutted and connectedto the sheath 21.

(b) of FIG. 4 is a perspective view showing the sleeve 30. The sleeve 30is a cylindrical member that is configured to have substantially thesame outer diameter and inner diameter as the sheath 21.

The sleeve 30 is abutted and connected to the sheath 21, thereby formingthe sheath 11, together with the sheath 21.

As shown in (c) of FIG. 4, before the sleeve 30 and the sheath 21 areconnected to each other, one end face 21 a of the sheath 21 and one endface 30 a of the sleeve 30 are brought close to each other, and theleading end portions of the pair of thermocouple elements 10 a and 10 bare inserted into the hole portion 11 b from inside of the sleeve 30.

Then, as shown in (a) of FIG. 5, the one end face 21 a of the sheath 21after the leading end section 22 has been removed and the one end face30 a of the sleeve 30 are abutted to each other, and the entireperiphery thereof is welded, whereby the sheath 21 and the sleeve 30 areconnected to each other. As a result, the sheath 11 can be obtained.

Next, the leading ends of the pair of thermocouple elements 10 a and 10b inserted in the hole portion 11 b are welded to each other to form aweld portion, and the temperature measuring junction 10 c is formed asthis weld portion. In addition, the hole portion 11 b is sealed by thisweld portion.

The temperature measuring junction 10 c is formed so as to be exposed ata side face 30 b of the sleeve 30. In addition, the temperaturemeasuring junction 10 c is formed in a shape in which the portions, ofthe leading ends of the pair of thermocouple elements 10 a and 10 b,that protrude from the side face 30 b of the sleeve 30, and excess weldmetal of the welding are cut off, and which allows the temperaturemeasuring junction 10 c to come into contact with the surface p1 of thepipe P when the obtained sheathed thermocouple 3 is accommodated in thepad 2.

Further, the inorganic insulating powder 12 is filled into the sleeve 30from the other end face 30 c of the sleeve 30.

The other end face 30 c of the sleeve 30 serves as the leading end face11 a of the sheath 11.

Next, as shown in (b) of FIG. 5, the sealing member 13 for sealing theother end face 30 c of the sleeve 30 is welded to the other end face 30c over the entire periphery thereof, whereby the sealing member 13 isfixed to the sleeve 30 (the sheath 11).

In this manner, the sheathed thermocouple 3 in which the temperaturemeasuring junction 10 c is provided so as to be exposed at the side face11 c of the sheath 11 can be produced.

According to the method for producing the sheathed thermocouple 3 asconfigured above, the leading end portions of the pair of thermocoupleelements 10 a and 10 b are caused to be exposed, the pair ofthermocouple elements 10 a and 10 b are inserted from inside of thesleeve 30 into the hole portion 11 b formed in the sleeve 30 (secondsheath member), and then, the sheath 21 (first sheath member) and thesleeve 30 are welded to each other. Then, the leading ends of the pairof thermocouple elements 10 a and 10 b are welded so as to seal the holeportion 11 b of the sleeve 30, whereby the temperature measuringjunction is formed. Therefore, for example, when compared with a casewhere work is performed while the pair of thermocouple elements 10 a and10 b are handled within the sheath 11 without the pair of thermocoupleelements 10 a and 10 b being exposed to the outside, workability at thetime of forming the temperature measuring junction 10 c exposed at theside face 11 c of the sheath 11 is good, and thus, production efficiencycan be improved.

FIG. 6 is a perspective view showing a leading end portion 4 of asheathed thermocouple 3 of a pad-equipped thermocouple according to asecond embodiment.

(a) of FIG. 6 is a perspective view showing the leading end portion 4 ofthe sheathed thermocouple 3 of a pad-equipped thermocouple according toa second embodiment, (b) of FIG. 6 is a perspective view showing theleading end portion 4 of the sheathed thermocouple 3 of a pad-equippedthermocouple according to a first modification of the second embodiment,and (c) of FIG. 6 is a perspective view showing the leading end portion4 of the sheathed thermocouple 3 of a pad-equipped thermocoupleaccording to a second modification of the second embodiment.

FIG. 7 is a cross-sectional view of the part in FIG. 6, that correspondsto the part along the A-A arrows in FIG. 2.

(a) of FIG. 7 is a cross-sectional view of the part, in (a) of FIG. 6,that corresponds to the part along the A-A arrows in FIG. 2, (b) of FIG.7 is a cross-sectional view of the part, in (b) of FIG. 6, thatcorresponds to the part along the A-A arrows in FIG. 2, and (c) of FIG.7 is a cross-sectional view of the part, in (c) of FIG. 6, thatcorresponds to the part along the A-A arrows in FIG. 2.

A pad-equipped thermocouple 1 of the second embodiment is different fromthat of the first embodiment in that: the outer peripheral shape of thesleeve 30 forming the leading end portion 4 of the sheathed thermocouple3 is a deformed shape which is not a circular shape; and the innerperipheral shape of the accommodation portion 2 a is a deformed shapecorresponding to the sleeve 30.

As shown in (a) of FIG. 6, the outer peripheral shape of the sleeve 30of the second embodiment is a substantially square shape.

The sleeve 30 has formed therein a through-hole 31 which penetrates thesleeve 30 along the longitudinal direction. The inner diameter of thethrough-hole 31 is substantially the same as the inner diameter of thesheath 21.

The hole portion 11 b closed by the temperature measuring junction 10 cis formed in the side face 30 b which is in contact with the surface p1of the pipe P.

The sleeve 30 is abutted and connected to the sheath 21 such that thethrough-hole 31 and the inner peripheral face of the sheath 21 areconnected to each other. Accordingly, the sleeve 30 and the sheath 21form the sheath 11 in which: the respective inner spaces of the sleeve30 and the sheath 21 are connected to each other; and the resultantinner space is filled with the inorganic insulating powder 12.

That is, the sheathed thermocouple 3 of the second embodiment isproduced by: making the outer peripheral shape of the sleeve 30, whichforms the leading end portion 4 of the sheathed thermocouple 3, into adeformed shape (square shape) which is not a circular shape; welding thesleeve 30 and the sheath 21 which has a circular shape to each other toform the sheath 11; and forming the temperature measuring junction 10 cexposed from the hole portion 11 b to the sheath surface.

As shown in (a) of FIG. 7, the accommodation portion 2 a of the pad 2 ofthe second embodiment is formed in a shape of a recessed groove in across section, the recessed groove extending along the longitudinaldirection of the sheath 11. The accommodation portion 2 a having thegroove shape is formed so as to be recessed from the contact face 2 b.

The pad 2 is welded and fixed in a state where the contact face 2 b isin contact with the surface p1 of the pipe P. Accordingly, theaccommodation portion 2 a is closed at the contact face 2 b side by thesurface p1 of the pipe P, and is in a hole shape having a substantiallysquare inner peripheral shape. Accordingly, the inner peripheral shapeof the accommodation portion 2 a is a shape that corresponds to theouter peripheral shape of the sleeve 30 forming the leading end portion4 of the sheathed thermocouple 3.

Between the inner peripheral face of the accommodation portion 2 a andthe outer peripheral face of the sleeve 30 in the leading end portion 4,a clearance is provided that allows the sheathed thermocouple 3 to beinserted into and pulled out from the accommodation portion 2 a alongthe surface p1 of the pipe P. Thus, while holding the sheathedthermocouple 3, the accommodation portion 2 a prevents the leading endportion 4 of the sheathed thermocouple 3 from rotating about the axisextending along the longitudinal direction.

Since the accommodation portion 2 a of the second embodiment is formedin a groove shape, the accommodation portion 2 a holds the sleeve 30 ina state where the side face 30 b of the sleeve 30 is exposed from theexposure opening 2 c to the surface p1 of the pipe P, and thetemperature measuring junction 10 c is in contact with the surface p1 ofthe pipe P.

In the second embodiment, the outer peripheral shape of the sleeve 30forming the leading end portion 4 of the sheathed thermocouple 3 is asquare shape, and the inner peripheral shape of the accommodationportion 2 a is a square shape corresponding to the sleeve 30, as a shapethat can prevent the leading end portion 4 from rotating about the axisextending along the longitudinal direction. Therefore, the temperaturemeasuring junction 10 c can be caused to be reliably in contact with thesurface p1 of the pipe P. As a result, the surface temperature of thepipe P can be more accurately measured.

In the second embodiment, when the sheathed thermocouple 3 is to beproduced, the sheath 21 having a circular shape and the sleeve 30 havinga square shape which prevents rotation of the sheathed thermocouple 3when the sheathed thermocouple 3 is accommodated in the accommodationportion 2 a are welded to each other to form the sheath 11. Therefore,it is possible to reduce the man-hour of work that is necessary forinstalling the sheathed thermocouple 3 such that the sheathedthermocouple 3 is in contact with the surface p1 of the pipe P and isprevented from rotating about the axis extending along the longitudinaldirection.

Although the outer peripheral shape of the sleeve 30 of the secondembodiment is a substantially square shape, the side face 30 b facingthe surface p1 side of the pipe P may be formed as a curved surface thatis slightly recessed so as to correspond to the surface p1 of the pipeP.

Accordingly, substantially the entirety of the side face 30 b of thesleeve 30 can be caused to be in contact with the surface p1 of the pipeP, and the temperature measuring junction 10 c can be caused to be morereliably in contact with the surface p1 of the pipe P.

In the second embodiment, a case where the outer peripheral shape of thesleeve 30 is formed in a substantially square shape has been shown as anexample. However, as shown in (b) of FIG. 6 and (b) of FIG. 7, the outerperipheral shape of the sleeve 30 may be an elliptical shape. Also inthis first modification, if the inner peripheral shape of theaccommodation portion 2 a is made to be a shape that corresponds to theouter peripheral shape of the sleeve 30, the leading end portion 4 canbe prevented from rotating about the axis extending along thelongitudinal direction.

As shown in (c) of FIG. 6 and (c) of FIG. 7, the outer peripheral shapeof the sleeve 30 may be a shape obtained by combining a semicircle and arectangle. Also in this second modification, if the inner peripheralshape of the accommodation portion 2 a is made to be a shape thatcorresponds to the outer peripheral shape of the sleeve 30, the leadingend portion 4 can be prevented from rotating about the axis extendingalong the longitudinal direction.

In this modification, similarly to the second embodiment, the side face30 b of the sleeve 30 is formed in a planar shape, but may be formed asa curved surface that is slightly recessed so as to correspond to thesurface p1 of the pipe P. Accordingly, the temperature measuringjunction 10 c can be caused to be more reliably in contact with thesurface p1 of the pipe P.

The outer peripheral shape of the sleeve 30 and the inner peripheralshape of the accommodation portion 2 a corresponding thereto may be anydeformed shape that is not a circular shape, and may be a closed curveshape other than a circular shape such as an ellipse, a shape obtainedby cutting off a part of a circular shape, a polygonal shape such as atriangle or a pentagon, a protruding type, a recessed type, and a shapeobtained by combining these. Further, a shape having a protrudingportion or a recessed portion which prevents rotation may be employed.

In the second embodiment described above, a case has been shown as anexample in which the outer peripheral shape of the sleeve 30 is made tobe a deformed shape whereby a part of the leading end portion 4 of thesheathed thermocouple 3 is made to have a deformed shape. However, theentirety of the leading end portion 4 may have a deformed shape, or theentirety, in the longitudinal direction, of the sheathed thermocouple 3may have a deformed shape.

In the first embodiment described above, the sleeve 30 and the sheath 21forming the leading end portion of the sheathed thermocouple 3 arecylindrical members having the same outer diameter and inner diameterwith each other. However, a configuration in which the outer peripheralshape of the sleeve 30 is a polygonal shape as shown in (a) of FIG. 6,and the inner peripheral shape of the accommodation portion 2 a of thepad 2 is a polygonal shape that corresponds to the outer peripheralshape of the sleeve 30 as shown in (a) of FIG. 7, (the secondembodiment); a configuration in which the outer peripheral shape of thesleeve 30 is an elliptical shape as shown in (b) of FIG. 6, and theinner peripheral shape of the accommodation portion 2 a of the pad 2 isan elliptical shape that corresponds to the outer peripheral shape ofthe sleeve 30 as shown in (b) of FIG. 7 (the first modification of thesecond embodiment); or a configuration in which the outer peripheralshape of the sleeve 30 is a semicircular shape as shown in (c) of FIG. 6and the inner peripheral shape of the accommodation portion 2 a of thepad 2 is a semicircular shape that corresponds to the outer peripheralshape of the sleeve 30 as shown in (c) of FIG. 7 (the secondmodification of the second embodiment) may be employed. In this manner,the sheathed thermocouple 3 accommodated in the accommodation portion 2a of the pad 2 can be prevented from rotating about the axis extendingalong the longitudinal direction of the sleeve 30, and the temperaturemeasuring junction 10 c can be caused to be reliably in contact with thesurface p1 of the pipe P. The outer peripheral shape of the pad 2 is notlimited to a substantially fan shape, and may be a polygonal shape or asemicircular shape. In addition, a heat insulating member may beprovided at the outside of the pad 2, whereby entry of heat from outsidemay be restricted.

In the embodiments described above, a method has been shown in which thesealing member 13 having a substantially hemispherical shape for sealingthe other end face 30 c of the sleeve 30 having a cylindrical shape iswelded to the other end face 30 c for the entire periphery thereof,whereby the sealing member 13 is fixed to the sleeve 30. However, as thesealing member 13, the sealing member 13, as shown in (a), (b), and (c)of FIG. 6, that has a disc-like shape that closes the opening of theother end face 30 c of the sleeve 30 may be employed and the sealingmember 13 may fixed by welding, for the entire outer periphery thereof,to the sleeve 30. Further, the other end face 30 c may be sealed by amelted welding rod.

In FIG. 6, the sleeve 30 and the inorganic insulating powder 12 areexpressed in a transparent manner so as to show the disposed state ofthe thermocouple elements 10 a and 10 b, and the temperature measuringjunction 10 c in the inner space of the sleeve 30.

The present invention is not limited to the first embodiment and thesecond embodiment.

For example, in the first embodiment, a case has been shown as anexample in which the first bar-shaped portion 3 a including the leadingend portion 4 of the sheathed thermocouple 3 extends in a bar shapealong the axial direction of the pipe P, and the pad 2 has a shapeextending along the axial direction of the pipe P so as to correspond tothe leading end portion 4. However, for example, as shown in FIG. 8, thefirst bar-shaped portion 3 a may have a shape extending in a bar shapealong the circumferential direction of the pipe P and the pad 2 may alsohave a shape extending along the circumferential direction of the pipe Pso as to correspond to the first bar-shaped portion 3 a.

In the embodiments described above, a case has been shown as an examplein which a pair of thermocouple elements 10 a and 10 b are accommodatedin the sheathed thermocouple 3. However, a plurality of pairs ofthermocouple elements may be accommodated in the sheathed thermocouple3.

In the embodiments described above, a case has been shown as an examplein which the pad-equipped thermocouple 1 is mounted to the surface p1 ofthe cylindrical pipe P as a temperature measurement target object.However, the pad-equipped thermocouple 1 can be mounted to a sphericalsurface part of a spherical structure, and also can be mounted to aplanar part of a box-shaped structure.

REFERENCE SIGNS LIST

-   -   1 pad-equipped thermocouple    -   2 pad    -   2 a accommodation portion    -   2 b contact face    -   2 c exposure opening    -   3 sheathed thermocouple    -   3 a first bar-shaped portion    -   3 b second bar-shaped portion    -   3 c third bar-shaped portion    -   4 leading end portion    -   5 first sheath fixing plate    -   5 a weld portion    -   6 second sheath fixing plate    -   6 a weld portion    -   10 a thermocouple element at positive side    -   10 b thermocouple element at negative side    -   10 c temperature measuring junction    -   11 sheath    -   11 a leading end face    -   11 b hole portion    -   11 c side face    -   11 c 1 abutment face    -   11 d opening    -   12 inorganic insulating powder    -   13 sealing member    -   20 sheathed thermocouple base material    -   21 sheath    -   21 a one end face    -   22 leading end section    -   30 sleeve    -   30 a one end face    -   30 b side face    -   30 c other end face    -   31 through-hole    -   B weld bead    -   P pipe    -   p1 surface

1. A pad-equipped thermocouple comprising: a sheathed thermocouple inwhich at least a pair of thermocouple elements and an insulating powderfor holding the thermocouple elements are accommodated in a sheath, andan opening in a leading end of the sheath is sealed by a sealing memberbeing welded to the leading end of the sheath; and a pad welded to atemperature measurement target object and configured to hold thesheathed thermocouple at a surface of the temperature measurement targetobject, wherein a temperature measuring junction formed by the pair ofthermocouple elements is provided so as to be exposed at a sheath sideface of a leading end portion of the sheathed thermocouple, the padincludes an accommodation portion configured to accommodate the leadingend portion of the sheathed thermocouple such that the leading endportion can be inserted into and pulled out from the accommodationportion along the surface of the temperature measurement target object,and the accommodation portion accommodates the leading end portion ofthe sheathed thermocouple in a state where the temperature measuringjunction and the surface of the temperature measurement target objectare in contact with each other, wherein the sheathed thermocoupleincludes: a first bar-shaped portion having, at one end thereof, theleading end portion; and a second bar-shaped portion connected to another end of the first bar-shaped portion and extending in a directionthat crosses an extending direction of the first bar-shaped portion in astate where the second bar-shaped portion is in contact with thetemperature measurement target object, and the pad-equipped thermocouplefurther comprises a fixing plate configured to fix the second bar-shapedportion to the surface of the temperature measurement target object,thereby preventing the first bar-shaped portion from rotating about anaxis extending along a longitudinal direction.
 2. The pad-equippedthermocouple according to claim 1, wherein the sheath side face of theleading end portion of the sheathed thermocouple has formed therein ahole portion for allowing the temperature measuring junction to beexposed therethrough, the hole portion is formed at a predeterminedinterval from an end face of the leading end, of the sheath, which hasthe sealing member welded thereto, the temperature measuring junction isformed as a weld portion obtained by welding leading ends of the pair ofthermocouple elements to each other, and the hole portion is sealed bythe weld portion.
 3. (canceled)
 4. A pad-equipped thermocouplecomprising: a sheathed thermocouple in which at least a pair ofthermocouple elements and an insulating powder for holding thethermocouple elements are accommodated in a sheath, and an opening in aleading end of the sheath is sealed by a sealing member being welded tothe leading end of the sheath; and a pad welded to a temperaturemeasurement target object and configured to hold the sheathedthermocouple at a surface of the temperature measurement target object,wherein a temperature measuring junction formed by the pair ofthermocouple elements is provided so as to be exposed at a sheath sideface of a leading end portion of the sheathed thermocouple, the padincludes an accommodation portion configured to accommodate the leadingend portion of the sheathed thermocouple such that the leading endportion can be inserted into and pulled out from the accommodationportion along the surface of the temperature measurement target object,the accommodation portion accommodates the leading end portion of thesheathed thermocouple in a state where the temperature measuringjunction and the surface of the temperature measurement target objectare in contact with each other, the leading end portion has an outerperipheral shape which is a deformed shape which is not a circularshape, and the accommodation portion has an inner peripheral shape whichis a shape that corresponds to the outer peripheral shape of the leadingend portion, thereby preventing the leading end portion from rotatingabout an axis extending along a longitudinal direction.
 5. Thepad-equipped thermocouple according to claim 4, wherein the innerperipheral shape of the accommodation portion and the outer peripheralshape of the leading end portion of the sheathed thermocouple are eachformed in any of a closed curve shape other than a circular shape, asemicircular shape, and a polygonal shape, and the inner peripheralshape of the accommodation portion and the outer peripheral shape of theleading end portion of the sheathed thermocouple are made to be the samewith each other so as not to cause a gap between an inner peripheralface of the accommodation portion and an outer peripheral face of theleading end portion of the sheathed thermocouple and the accommodationportion and the leading end portion are fitted to each other, wherebythe accommodation portion prevents the leading end portion of thesheathed thermocouple from rotating about the axis extending along thelongitudinal direction.
 6. (canceled)
 7. The pad-equipped thermocoupleaccording to claim 4, wherein the sheath side face of the leading endportion of the sheathed thermocouple has formed therein a hole portionfor allowing the temperature measuring junction to be exposedtherethrough, the hole portion is formed at a predetermined intervalfrom an end face of the leading end, of the sheath, which has thesealing member welded thereto, the temperature measuring junction isformed as a weld portion obtained by welding leading ends of the pair ofthermocouple elements to each other, and the hole portion is sealed bythe weld portion.
 8. The pad-equipped thermocouple according to claim 5,wherein the sheath side face of the leading end portion of the sheathedthermocouple has formed therein a hole portion for allowing thetemperature measuring junction to be exposed therethrough, the holeportion is formed at a predetermined interval from an end face of theleading end, of the sheath, which has the sealing member welded thereto,the temperature measuring junction is formed as a weld portion obtainedby welding leading ends of the pair of thermocouple elements to eachother, and the hole portion is sealed by the weld portion.